The present invention relates to a calorimeter for measuring the energy transported or transmitted by electromagnetic radiation (light, X, laser, etc.) or by a particle flux. It is more particularly used in optoelectronics in measuring pulse-type photon energy transported by laser radiation.
Calorimeters are known in which measurement takes place of the temperature increase produced by the interaction of electromagnetic radiation and a material able to absorb said radiation and the energy transported by the radiation is deduced from this measurement. Generally such calorimeters comprise a radiation absorbing element having an outer face exposed to the radiation and an inner face. The absorbing element undergoes a temperature increase during the interaction with the radiation. A thermopile having a measuring face in contact with the inner face of the absorbing element and a reference face kept at reference temperature supplies a potential difference proportional to the temperature difference between its measuring and reference faces. These calorimeters are generally equipped with calibration means, which can comprise a resistance wire adhered to the inner face of the absorbing element or to the peripherary thereof. The function of this wire is to simulate an energy "deposit" of a clearly defined value by heating the absorbing element through the passage of electric current, thus permitting the calibration of the calorimeter. FR-A- No. 2 050 603 describes such a calorimeter.
Such calorimeters suffer from several disadvantages. Firstly the sensitivity is low, because the thermopile covers virtually the entire inner face of the absorbing element and consequently has a high calorific capacity compared with that of the absorbing element. Moreover, calibration is not very reliable, because the simulation of the energy deposit by electric heating of the resistance wire is not satisfactory, the wire only covering a small part of the inner face of the absorbing element or is placed on its peripherary. Finally, calibration is difficult and not very reproducible, because the operation of gluing the wire to the inner face or peripherary of the absorbing element is difficult and not very effective, because at certain points the wire can become unstuck.